Shackle



FIG. 1 is a front perspective view of the shackle;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a front view thereof, with the back view being a mirror image of; and,

FIG. 5 is a left side view thereof, with the right side view being a mirror image of.

The broken lines in the drawings illustrate portions of the shackle and form no part of the claimed design. 

CLAIM The ornamental design for a shackle, as shown and described. 